I did mine through trademarkia.com
TESS is a good start but did not catch a potential problem that our lawyer did where we had to exclude "footwear." It only costs about $175 (there are different package prices, but this is the best value IMO and what we did) for them to do it as long as there are no additional hiccups. The $275 fee is non-refundable. If you are denied, you are just out of luck.
It will take close to 9 months or a year to get the trademark if everything goes well.
Everything Zoocity said seems about right. One class often covers quite a bit though. Here is our class: IC 025. US 022 039. G & S: Clothing, namely, tops, bottoms, sweatshirts, hats, Hooded sweatshirts; T-shirts, jackets, excluding footwear.
You should have a logo or proof of use ready before you file. It's a "specimen" you have to submit, don't try to fake this, you'll probably get called out.